Eleocharis tortilis differs consistently from E. tuberculosa only in tubercle size. Most specimens of E. tortilis have culms that are sharply trigonous and no more than 0.5 mm wide. However, about two-thirds of the specimens of E. tortilis from Texas resemble E. tuberculosa in having culms that are elliptic or subelliptic in cross section and that sometimes reach 1 mm wide. Those elliptic-culmed plants may deserve taxonomic recognition. I have not seen voucher specimens for reports in the literature (H. K. Svenson 1937; M. L. Brown and R. G. Brown 1984) for Alabama (Mobile, 1800s), Delaware (1908), Maryland (1863–1878), and New York (Long Island, 1903).